1. Field of the Invention
The present invention relates to internal combustion engines. More particularly, the invention relates to an improved, lightweight four-stroke internal combustion engine having a favorable power to weight ratio and improved adaptability to varying applications.
2. Related Art
It is often desirable in many applications to provide an engine which is reliable, powerful, lightweight, and easily adaptable to different applications. Four-stroke engines are often considered more reliable than two-stroke engines, but often include a lower power density; that is, the unit weight to power output ratio is often higher than for two-stroke engines. Particular applications can benefit from reliable, lightweight four-stroke engines, such as in cases where operator and public safety are of heightened concern. Such applications can include motorized crafts utilized in aviation, military, and recreational applications.
The need for safety appears to be a conflicting goal with providing more power for a given engine weight, as two-stroke engines generally provide more power for the same engine weight. For example, in aircraft, recreational vehicles, portable power equipment, and the like, two-stroke engines are often used due to the desire for limited weight, but reliability of two-stroke engine has been recognized as a problem.
Further, it is desirable in many cases to adapt an engine design to a new application. However, this may involve reversing the intake and exhaust sides to flip the engine front to back or to accommodate the engine in a particular vehicle or apparatus. It may further involve reversing engine rotation direction; that is, reverse rotation direction from a counterclockwise to a clockwise direction, or the inverse. While many engines can be easily rotated about a horizontal axis, a vertically rotated mounting may be desired instead. Such changes typically involve considerable customization and engineering modification which cannot be done by a customer, but rather requires the manufacturer's specialized knowledge and expertise.